A related connector device is known from U.S. Pat. No. 7,931,627 B2. The related connector device is provided as a Y port for a medical infusion system. A fluid flow chamber, which forms several channel portions, is arranged in a main housing. Two channel portions branch in two different directions towards a respective open attachment, which can be connected in each case to a hose line that leads to a catheter or to a fluid reservoir receptacle. Moreover, the main housing has an attachment port which, in a continuation of one channel portion, opens in an opposite direction and comprises a Luer connecting portion in order to be able to attach a corresponding Luer attachment part such as a syringe or a fluid reservoir receptacle. A flexible check valve is provided in the fluid flow chamber and is able to close one channel portion at the branch to the other channel portion inside the fluid flow chamber. The flexible, tab-like valve does not completely shut off this channel portion, and instead it merely reduces the flow through the channel portion.